bug: Do not record the GCM data overflow error

Return the GCM data overflow error to the subscription server, but
there's no need to record it into Sentry.

Closes #552

autopush/router/gcm.py

@@ -76,7 +76,7 @@ def _route(self, notification, uaid_data):
                                   "to 3070 bytes. Converted buffer too " +
                                   "long by %d bytes" %
                                   (len(notification.data) - mdata),
-                                  413, errno=104)
+                                  413, errno=104, log_exception=False)
 
             data['body'] = notification.data
             data['con'] = notification.headers['content-encoding']